package com.huawei;

import java.util.LinkedHashSet;
import java.util.Scanner;

public class HJ009 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        LinkedHashSet<String> set = new LinkedHashSet<>();

        String input = scanner.next();
        StringBuilder sb = new StringBuilder(input);
        sb.reverse();
        while(sb.length() != 0){
            set.add(sb.substring(0,1));
            sb.delete(0,1);
        }
        for (String s : set) {
            System.out.print(s);
        }
    }
}
